We didn't add any yet to the house we built, but we had blocking added to all the shower walls, placed approximately 36" from the floor. I should probably add some grab bars soon to the guest shower my parents use when visiting.

Absolutely agree that it's tough to know until the need arises, but there is general guidance with that. In our last home, we had my FIL move in . It was an au pair or in law's suite so perfect- first floor, had its own bathroom. We had remodled and removed the tub and had a shower. We did not know about grab bars ( we did the remodel several years before he moved in). Of course, he ended up using the towel bar and the shower doors. Not a good thing. The towel bar came right out of the wall the shower door was kind of messed up after. We learned then that we needed to have extra blocking and were ablet o put one by the toilet as well. I'm trying to see what makes sense for our layout, without having it excessive. The video was very good explaining that at entry it should be vertical and within the shower a bit more variable but horizontal.. and so on

Your grab bar looks similar to the Delta 41624 grab bar. As you can see on page 1 of the installation instructions, the grab bar is shipped with flat head wood screws.* If you look at the drawing in the upper left-hand corner of page 6, you see that the part into which the grab bar is inserted is attached to the hollow-wall anchor with flat-head screws. The cover then hides the screw heads. (*As described in step 2, the hollow-wall anchor would not have been used if the grab bar was attached to a stud. Instead, you would have followed the instructions on page 2, steps 1 a, b,c, and used the supplied flat-head wood screws to attach the flange to the studs. Then the cover would have been pushed into place to cover the screws.)

Yes absolutely we are aware that not just any bar can be installed any which way. When we had my FIL move in with us in our last house, he grabbed a towel bar to steady himself. He didn't get hurt but that was how we learned. We had the correct blocking done to install safety bars for him. Since this is a remodel renovation, we had the safety bars factored in from the get go. When I say we are figuring out what bars where, ti's because we do have some options with shower entry etc. And yes, we are using the guidelines to determine.